Serine proteases are a subgroup of carbonyl hydrolases. They comprise a diverse class of enzymes having a wide range of specificities and biological functions. Stroud, R. Sci. Amer., 131:74-88. Despite their functional diversity, the catalytic machinery of serine proteases has been approached by at least two genetically distinct families of enzymes: 1) the subtilisins and 2) the mammalian chymotrypsin-related and homologous bacterial serine proteases (e.g., trypsin and S. gresius trypsin). These two families of serine proteases show remarkably similar mechanisms of catalysis. Kraut, J. (1977), Annu. Rev. Biochem., 46:331-358. Furthermore, although the primary structure is unrelated, the tertiary structure of these two enzyme families bring together a conserved catalytic triad of amino acids consisting of serine, histidine and aspartate.
Subtilisins are serine proteases (approx. MW 27,500) which are secreted in large amounts from a wide variety of Bacillus species and other microorganisms. The protein sequence of subtilisin has been determined from at least nine different species of Bacillus. Markland, F. S., et al. (1983), Hoppe-Seyler""s Z. Physiol. Chem., 364:1537-1540. The three-dimensional crystallographic structure of subtilisins from Bacillus amyloliquefaciens, Bacillus licheniforimis and several natural variants of B. lentus have been reported. These studies indicate that although subtilisin is genetically unrelated to the mammalian serine proteases, it has a similar active site structure. The x-ray crystal structures of subtilisin containing covalently bound peptide inhibitors (Robertus, J. D., et al. (1972), Biochemistry, 11:2439-2449) or product complexes (Robertus, J. D., et al. (1976), J. Biol. Chem., 251:1097-1103) have also provided information regarding the active site and putative substrate binding cleft of subtilisin. In addition, a large number of kinetic and chemical modification studies have been reported for subtilisin; Svendsen, B. (1976), Carlsberg Res. Commun., 41:237-291; Markland, F. S. Id.) as well as at least one report wherein the side chain of methionine at residue 222 of subtilisin was converted by hydrogen peroxide to methionine-sulfoxide (Stauffer, D. C., et al. (1965), J. Biol. Chem., 244:5333-5338) and extensive site-specific mutagenesis has been carried out (Wells and Estell (1988) TIBS 13:291-297)
It is an object herein to provide protease variants containing a substitution of an amino acid at a residue position corresponding to position 103 of Bacillus amyloliquefaciens subtilisin and substituting one or more amino acids at residue positions selected from the group consisting of residue positions corresponding to positions 1, 3, 4, 8, 10, 12, 13, 16, 17, 18, 19, 20, 21, 22, 24, 27, 33, 37, 38, 42, 43, 48, 55, 57, 58, 61, 62, 68, 72, 75, 76, 77, 78, 79, 86, 87, 89, 97, 98, 99, 101, 102, 104, 106, 107, 109, 111, 114, 116, 117, 119, 121, 123, 126, 128, 130, 131, 133, 134, 137, 140, 141, 142, 146, 147, 158, 159, 160, 166, 167, 170, 173, 174, 177, 181, 182, 183, 184, 185, 188, 192, 194, 198, 203, 204, 205, 206, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 222, 224, 227, 228, 230, 232, 236, 237, 238, 240, 242, 243, 244, 245, 246, 247, 248, 249, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 265, 268, 269, 270, 271, 272, 274 and 275 of Bacillus amyloliquefaciens subtilisin; wherein when a substitution at a position corresponding to residue position 103 is combined with a substitution at a position corresponding to residue position 76, there is also a substitution at one or more residue positions other than residue positions corresponding to positions 27, 99, 101, 104, 107, 109, 123, 128, 166, 204, 206, 210, 216, 217, 218, 222, 260, 265, or 274 of Bacillus amyloliquefaciens subtilisin.
While any combination of the above listed amino acid substitutions may be employed, the preferred protease variant enzymes useful for the present invention comprise the substitution of amino acid residues in the following combinations of positions. All of the residue positions correspond to positions of Bacillus amyloliquefaciens subtilisin:
(1) a protease variant including substitutions of the amino acid residues at position 103 and at one or more of the following positions 236 and 245;
(2) a protease variant including substitutions of the amino acid residues at positions 103 and 236 and at one or more of the following positions 1, 9, 12, 61, 62, 68, 76, 97, 98, 101, 102, 104, 109, 130, 131, 159, 183, 185, 205, 209, 210, 211, 212, 213, 215, 217, 230, 232, 248, 252, 257, 260, 270 and 275;
(3) a protease variant including substitutions of the amino acid residues at positions 103 and 245 and at one or more of the following positions 1, 9, 12, 61, 62, 68, 76, 97, 98, 101, 102, 104, 109, 130, 131, 159, 170, 183, 185, 205, 209, 210, 211, 212, 213, 215, 217, 222, 230, 232, 248, 252, 257, 260, 261, 270 and 275; or
(4) a protease variant including substitutions of the amino acid residues at positions 103, 236 and 245 and at one or more of the following positions 1, 9, 12, 61, 62, 68, 76, 97, 98, 101, 102, 104, 109, 130, 131, 159, 183, 185, 205, 209, 210, 211, 212, 213, 215, 217, 230, 232, 243, 248, 252, 257, 260, 270 and 275.
More preferred protease variants are substitution sets selected from the group consisting of residue positions corresponding to positions in Table 1 of Bacillus amyloliquefaciens subtilisin:
Most preferred protease variants are those shown in Table 3.
It is a further object to provide DNA sequences encoding such protease variants, as well as expression vectors containing such variant DNA sequences.
Still further, another object of the invention is to provide host cells transformed with such vectors, as well as host cells which are capable of expressing such DNA to produce protease variants either intracellularly or extracellularly.
There is further provided a cleaning composition comprising a protease variant of the present invention.
Additionally, there is provided an animal feed comprising a protease variant of the present invention.
Also provided is a composition for the treatment of a textile comprising a protease variant of the present invention.